Having forgotten his keys, Tamao Hiroi, a high-school student, returns home using the back entrance and is surprised to find a stranger in his bed. Soon he realizes this is no stranger but Ran Homura, one year younger, softball ace and one of the most beautiful girls at school! Hiroi watches her masturbating on his bed and instinctively does the same, peeking through the glass door. He is soon found out and a strange 'master/slave' relationship begins.